[LLVMdev] AllocaInst for FunctionType?

[Alexander Poddey]

> As far as I understand, an alloca instruction allocate space for a
> variable. It does not really make sense for it to be used with a function
> type (do you want to store a pointer to a function of this type?).

Yes. if I undertand correctly, alloca allocates space for a variable.
I could then want to allocate space for a function pointer.

I can now see code similar to my example by using c function pointers and 
emitting c++API code:


When translating c++ code using function pointers, the emitted llvm for 

int (*foo2)(double,float);

looks like

%foo2 = alloca i32 (double, float)*, align 8

and the c++ API code (generated by llc -march=cpp) 



std::vector<Type*>FuncTy_49_args;
 FuncTy_49_args.push_back(Type::getDoubleTy(mod->getContext()));
 FuncTy_49_args.push_back(Type::getFloatTy(mod->getContext()));
 FunctionType* FuncTy_49 = FunctionType::get(
  /*Result=*/IntegerType::get(mod->getContext(), 32),
  /*Params=*/FuncTy_49_args,
  /*isVarArg=*/false);
 
PointerType* PointerTy_48 = PointerType::get(FuncTy_49, 0);
 
AllocaInst* ptr_foo2 = new AllocaInst(PointerTy_48, "foo2", label_entry_71);


This is what I had in my 1st post. So this seems to be the way to do it.
This vice versa transformation between source, IR and API is quite cool!


Alex